The phrase "are difficult to acquire" is correct and usable in written English.
It can be used when discussing items, skills, or knowledge that are not easily obtained or learned.
Example: "Certain rare artifacts are difficult to acquire due to their limited availability and high demand."
Alternatives: "are hard to obtain" or "are challenging to secure."
Full logographic systems such as Chinese or mixed systems such as Japanese are difficult to acquire because they require the memorization of thousands of distinctive characters.
As of mid-December, 9,133 had passed — the newest foot soldiers in a real estate market in which prices are down, sales are sluggish and mortgages are difficult to acquire.
Hard technologies cannot be successful without the corresponding soft technologies; however, the latter are difficult to acquire because they depend on human knowledge that is obtained through formal training, experience, and textbooks.
What makes him "mad" he says, is the notion that a newspaper is merely "a monopoly protected by printing press and that the thing being called a journalist is the chance to write the news, as if there isn't this separate set of skills that are difficult to acquire and worthy of preservation.
To do that, investigators would need to study the brains of players who do not develop C.T.E., and those are difficult to acquire because families of former players who do not exhibit symptoms are less likely to donate their brains to science.
Such skills are difficult to acquire, and to document, during academic training.
They're difficult to acquire and expensive to raise.
"It's difficult to acquire a quality big man in this league," Thomas said in a conference call yesterday.
"It's difficult to acquire assets in Russia these days if you're not a Russian company".
One reason is that it is difficult to acquire and use the complicated gear needed to make and scatter deadly pathogens.
To be charitable, perspective may be difficult to acquire when one is born into a distinguished military family, and rises to the rank of Commandant of the US Marine Corps.
